lib/obstack.c

   1 /* obstack.c - subroutines used implicitly by object stack macros
   2    Copyright (C) 1988-2025 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation, either version 3 of the
   8    License, or (at your option) any later version.
   9
  10    This file is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18
  19 #ifdef _LIBC
  20 # include <obstack.h>
  21 #else
  22 # include <config.h>
  23 # include "obstack.h"
  24 #endif
  25
  26 /* NOTE BEFORE MODIFYING THIS FILE IN GNU LIBC: _OBSTACK_INTERFACE_VERSION in
  27    gnu-versions.h must be incremented whenever callers compiled using an old
  28    obstack.h can no longer properly call the functions in this file.  */
  29
  30 /* If GCC, or if an oddball (testing?) host that #defines __alignof__,
  31    use the already-supplied __alignof__.  Otherwise, this must be Gnulib
  32    (as glibc assumes GCC); defer to Gnulib's alignof_type.  */
  33 #if !defined __GNUC__ && !defined __alignof__
  34 # include <alignof.h>
  35 # define __alignof__(type) alignof_type (type)
  36 #endif
  37 #include <stdlib.h>
  38 #include <stdint.h>
  39
  40 #ifndef MAX
  41 # define MAX(a,b) ((a) > (b) ? (a) : (b))
  42 #endif
  43
  44 /* Determine default alignment.  */
  45
  46 /* If malloc were really smart, it would round addresses to DEFAULT_ALIGNMENT.
  47    But in fact it might be less smart and round addresses to as much as
  48    DEFAULT_ROUNDING.  So we prepare for it to do that.
  49
  50    DEFAULT_ALIGNMENT cannot be an enum constant; see gnulib's alignof.h.  */
  51 #define DEFAULT_ALIGNMENT MAX (__alignof__ (long double),                     \
  52                                MAX (__alignof__ (uintmax_t),                  \
  53                                     __alignof__ (void *)))
  54 #define DEFAULT_ROUNDING MAX (sizeof (long double),                           \
  55                                MAX (sizeof (uintmax_t),                       \
  56                                     sizeof (void *)))
  57
  58 /* Call functions with either the traditional malloc/free calling
  59    interface, or the mmalloc/mfree interface (that adds an extra first
  60    argument), based on the value of use_extra_arg.  */
  61
  62 static void *
  63 call_chunkfun (struct obstack *h, size_t size)
  64 {
  65   if (h->use_extra_arg)
  66     return h->chunkfun.extra (h->extra_arg, size);
  67   else
  68     return h->chunkfun.plain (size);
  69 }
  70
  71 static void
  72 call_freefun (struct obstack *h, void *old_chunk)
  73 {
  74   if (h->use_extra_arg)
  75     h->freefun.extra (h->extra_arg, old_chunk);
  76   else
  77     h->freefun.plain (old_chunk);
  78 }
  79
  80
  81 /* Initialize an obstack H for use.  Specify chunk size SIZE (0 means default).
  82    Objects start on multiples of ALIGNMENT (0 means use default).
  83
  84    Return nonzero if successful, calls obstack_alloc_failed_handler if
  85    allocation fails.  */
  86
  87 static int
  88 _obstack_begin_worker (struct obstack *h,
  89                        _OBSTACK_SIZE_T size, _OBSTACK_SIZE_T alignment)
  90 {
  91   struct _obstack_chunk *chunk; /* points to new chunk */
  92
  93   if (alignment == 0)
  94     alignment = DEFAULT_ALIGNMENT;
  95   if (size == 0)
  96     /* Default size is what GNU malloc can fit in a 4096-byte block.  */
  97     {
  98       /* 12 is sizeof (mhead) and 4 is EXTRA from GNU malloc.
  99          Use the values for range checking, because if range checking is off,
 100          the extra bytes won't be missed terribly, but if range checking is on
 101          and we used a larger request, a whole extra 4096 bytes would be
 102          allocated.
 103
 104          These number are irrelevant to the new GNU malloc.  I suspect it is
 105          less sensitive to the size of the request.  */
 106       int extra = ((((12 + DEFAULT_ROUNDING - 1) & ~(DEFAULT_ROUNDING - 1))
 107                     + 4 + DEFAULT_ROUNDING - 1)
 108                    & ~(DEFAULT_ROUNDING - 1));
 109       size = 4096 - extra;
 110     }
 111
 112   h->chunk_size = size;
 113   h->alignment_mask = alignment - 1;
 114
 115   chunk = h->chunk = call_chunkfun (h, h->chunk_size);
 116   if (!chunk)
 117     (*obstack_alloc_failed_handler) ();
 118   h->next_free = h->object_base = __PTR_ALIGN ((char *) chunk, chunk->contents,
 119                                                alignment - 1);
 120   h->chunk_limit = chunk->limit = (char *) chunk + h->chunk_size;
 121   chunk->prev = NULL;
 122   /* The initial chunk now contains no empty object.  */
 123   h->maybe_empty_object = 0;
 124   h->alloc_failed = 0;
 125   return 1;
 126 }
 127
 128 int
 129 _obstack_begin (struct obstack *h,
 130                 _OBSTACK_SIZE_T size, _OBSTACK_SIZE_T alignment,
 131                 void *(*chunkfun) (size_t),
 132                 void (*freefun) (void *))
 133 {
 134   h->chunkfun.plain = chunkfun;
 135   h->freefun.plain = freefun;
 136   h->use_extra_arg = 0;
 137   return _obstack_begin_worker (h, size, alignment);
 138 }
 139
 140 int
 141 _obstack_begin_1 (struct obstack *h,
 142                   _OBSTACK_SIZE_T size, _OBSTACK_SIZE_T alignment,
 143                   void *(*chunkfun) (void *, size_t),
 144                   void (*freefun) (void *, void *),
 145                   void *arg)
 146 {
 147   h->chunkfun.extra = chunkfun;
 148   h->freefun.extra = freefun;
 149   h->extra_arg = arg;
 150   h->use_extra_arg = 1;
 151   return _obstack_begin_worker (h, size, alignment);
 152 }
 153
 154 /* Allocate a new current chunk for the obstack *H
 155    on the assumption that LENGTH bytes need to be added
 156    to the current object, or a new object of length LENGTH allocated.
 157    Copies any partial object from the end of the old chunk
 158    to the beginning of the new one.  */
 159
 160 void
 161 _obstack_newchunk (struct obstack *h, _OBSTACK_SIZE_T length)
 162 {
 163   struct _obstack_chunk *old_chunk = h->chunk;
 164   struct _obstack_chunk *new_chunk = NULL;
 165   size_t obj_size = h->next_free - h->object_base;
 166   char *object_base;
 167
 168   /* Compute size for new chunk.  */
 169   size_t sum1 = obj_size + length;
 170   size_t sum2 = sum1 + h->alignment_mask;
 171   size_t new_size = sum2 + (obj_size >> 3) + 100;
 172   if (new_size < sum2)
 173     new_size = sum2;
 174   if (new_size < h->chunk_size)
 175     new_size = h->chunk_size;
 176
 177   /* Allocate and initialize the new chunk.  */
 178   if (obj_size <= sum1 && sum1 <= sum2)
 179     new_chunk = call_chunkfun (h, new_size);
 180   if (!new_chunk)
 181     (*obstack_alloc_failed_handler)();
 182   h->chunk = new_chunk;
 183   new_chunk->prev = old_chunk;
 184   new_chunk->limit = h->chunk_limit = (char *) new_chunk + new_size;
 185
 186   /* Compute an aligned object_base in the new chunk */
 187   object_base =
 188     __PTR_ALIGN ((char *) new_chunk, new_chunk->contents, h->alignment_mask);
 189
 190   /* Move the existing object to the new chunk.  */
 191   memcpy (object_base, h->object_base, obj_size);
 192
 193   /* If the object just copied was the only data in OLD_CHUNK,
 194      free that chunk and remove it from the chain.
 195      But not if that chunk might contain an empty object.  */
 196   if (!h->maybe_empty_object
 197       && (h->object_base
 198           == __PTR_ALIGN ((char *) old_chunk, old_chunk->contents,
 199                           h->alignment_mask)))
 200     {
 201       new_chunk->prev = old_chunk->prev;
 202       call_freefun (h, old_chunk);
 203     }
 204
 205   h->object_base = object_base;
 206   h->next_free = h->object_base + obj_size;
 207   /* The new chunk certainly contains no empty object yet.  */
 208   h->maybe_empty_object = 0;
 209 }
 210
 211 /* Return nonzero if object OBJ has been allocated from obstack H.
 212    This is here for debugging.
 213    If you use it in a program, you are probably losing.  */
 214
 215 /* Suppress -Wmissing-prototypes warning.  We don't want to declare this in
 216    obstack.h because it is just for debugging.  */
 217 int _obstack_allocated_p (struct obstack *h, void *obj) __attribute_pure__;
 218
 219 int
 220 _obstack_allocated_p (struct obstack *h, void *obj)
 221 {
 222   struct _obstack_chunk *lp;    /* below addr of any objects in this chunk */
 223   struct _obstack_chunk *plp;   /* point to previous chunk if any */
 224
 225   lp = (h)->chunk;
 226   /* We use >= rather than > since the object cannot be exactly at
 227      the beginning of the chunk but might be an empty object exactly
 228      at the end of an adjacent chunk.  */
 229   while (lp != NULL && ((void *) lp >= obj || (void *) (lp)->limit < obj))
 230     {
 231       plp = lp->prev;
 232       lp = plp;
 233     }
 234   return lp != NULL;
 235 }
 236
 237 /* Free objects in obstack H, including OBJ and everything allocate
 238    more recently than OBJ.  If OBJ is zero, free everything in H.  */
 239
 240 void
 241 _obstack_free (struct obstack *h, void *obj)
 242 {
 243   struct _obstack_chunk *lp;    /* below addr of any objects in this chunk */
 244   struct _obstack_chunk *plp;   /* point to previous chunk if any */
 245
 246   lp = h->chunk;
 247   /* We use >= because there cannot be an object at the beginning of a chunk.
 248      But there can be an empty object at that address
 249      at the end of another chunk.  */
 250   while (lp != NULL && ((void *) lp >= obj || (void *) (lp)->limit < obj))
 251     {
 252       plp = lp->prev;
 253       call_freefun (h, lp);
 254       lp = plp;
 255       /* If we switch chunks, we can't tell whether the new current
 256          chunk contains an empty object, so assume that it may.  */
 257       h->maybe_empty_object = 1;
 258     }
 259   if (lp)
 260     {
 261       h->object_base = h->next_free = (char *) (obj);
 262       h->chunk_limit = lp->limit;
 263       h->chunk = lp;
 264     }
 265   else if (obj != NULL)
 266     /* obj is not in any of the chunks! */
 267     abort ();
 268 }
 269
 270 _OBSTACK_SIZE_T
 271 _obstack_memory_used (struct obstack *h)
 272 {
 273   struct _obstack_chunk *lp;
 274   _OBSTACK_SIZE_T nbytes = 0;
 275
 276   for (lp = h->chunk; lp != NULL; lp = lp->prev)
 277     {
 278       nbytes += lp->limit - (char *) lp;
 279     }
 280   return nbytes;
 281 }
 282
 283 #ifndef _OBSTACK_NO_ERROR_HANDLER
 284 /* Define the error handler.  */
 285 # include <stdio.h>
 286
 287 /* Exit value used when 'print_and_abort' is used.  */
 288 # ifdef _LIBC
 289 int obstack_exit_failure = EXIT_FAILURE;
 290 # else
 291 #  include "exitfail.h"
 292 #  define obstack_exit_failure exit_failure
 293 # endif
 294
 295 # ifdef _LIBC
 296 #  include <libintl.h>
 297 #  ifndef _
 298 #   define _(msgid) gettext (msgid)
 299 #  endif
 300 # else
 301 #  include "gettext.h"
 302 #  ifndef _
 303 #   define _(msgid) dgettext ("gnulib", msgid)
 304 #  endif
 305 # endif
 306
 307 # ifdef _LIBC
 308 #  include <libio/iolibio.h>
 309 # endif
 310
 311 static __attribute_noreturn__ void
 312 print_and_abort (void)
 313 {
 314   /* Don't change any of these strings.  Yes, it would be possible to add
 315      the newline to the string and use fputs or so.  But this must not
 316      happen because the "memory exhausted" message appears in other places
 317      like this and the translation should be reused instead of creating
 318      a very similar string which requires a separate translation.  */
 319 # ifdef _LIBC
 320   (void) __fxprintf (NULL, "%s\n", _("memory exhausted"));
 321 # else
 322   fprintf (stderr, "%s\n", _("memory exhausted"));
 323 # endif
 324   exit (obstack_exit_failure);
 325 }
 326
 327 /* The functions allocating more room by calling 'obstack_chunk_alloc'
 328    jump to the handler pointed to by 'obstack_alloc_failed_handler'.
 329    This can be set to a user defined function which should either
 330    abort gracefully or use longjump - but shouldn't return.  This
 331    variable by default points to the internal function
 332    'print_and_abort'.  */
 333 __attribute_noreturn__ void (*obstack_alloc_failed_handler) (void)
 334   = print_and_abort;
 335 #endif /* !_OBSTACK_NO_ERROR_HANDLER */